Over the years, a number of different types of thermoplastic polymers materials have been used to manufacture molds for forming ophthalmic lenses using various types of polymerizable lens-forming compositions and using various lens-making processes, including spin casting, lathing and cast molding.
U.S. Pat. No. 4,921,205 issued to Drew, Jr. et al., describes a process of making and machining lens blanks to form either soft or rigid gas permeable contact lenses. The process of Drew, Jr. involves specifically formulating a material for a mold member in order to cause the lens blank to strongly adhere to the mold member after curing. The process includes forming the mold member, casting a polymerizable lens blank into the mold member, heating the polymerizable lens blank and the mold member to polymerize or set the lens blank in the mold member to create an integral blank-mold member structure, and machining the integral blank-mold member structure by first machining away the softer mold member to reveal the lens blank, and then machining the lens blank to form a lens. Drew, Jr. et al. lists a number of types of conventional thermosetting or thermoplastic soft lens materials and rigid gas permeable lens materials that can be used in accordance with the disclosure, but does not discuss any silicone hydrogel materials. While Drew, Jr. et al. lists a number of types of polymers that can be used for the mold member including polybutylene terephthalate (PBT), only heat is used to cure or set the polymerizable lens blanks.
U.S. Pat. No. 6,075,066 issued to Matsuda et al., describes soft contact lenses made by crosslinking glycosoaminoglycan using photoirradiation in a single plastic mold, such as a PBT mold. The manufacturing methods described in Matsuda et al. include cut polishing, spin casting, pressing and molding, with spin casting being particularly preferred. In the spin-casting manufacturing method described, the lens forming material is crosslinked by directing UV light on the lens forming material while it remains in contact with the mold or after it has been separated from the single mold. In the case where the lens forming material is crosslinked while it remains in contact with the mold, as a single mold member is used the spin casting method, and the UV light is not directed through the single mold member in order to crosslink the lens forming material. If the lens forming material was crosslinked while in contact with the mold, the crosslinked lens and the mold are then soaked in an aqueous solution to swell the lens, allowing the lens to be detached from the single mold member used in the spin casting method.
U.S. Pat. No. 6,997,428 issued to Andino et al. is directed to contact lens molds made of a first UV transmissive section formed from a UV transmissive material which molds an optical surface of the lens, and a second UV opaque section formed from a UV opaque material which does not mold an optical surface of the lens. Andino et al. does not discuss any preference for mold materials beyond those that exhibit good adhesion to each other when the sections are combined to form a single mold member, and does not discuss the use of the molds to form any particular types of lens materials such as silicone hydrogels.
When contact lens mold assemblies made of thermoplastic polymer having high levels of UV light transmission such as polypropylene and ethylene-vinyl alcohol copolymers are used to cast mold silicone hydrogel contact lenses, it is common to use UV light to cure the polymerizable lens-forming composition to form a lens body. However, use of these thermoplastic polymers having high levels of UV light transmittance can present problems. For example, silicone hydrogel contact lens bodies cast molded in polypropylene typically require additional processing steps such as surface plasma treatments in order to make the lens surfaces adequately wettable, increasing the cost of manufacturing the lenses. Some polar thermoplastic polymers such as EVOH can be used to form mold members which produce silicone hydrogel lens bodies having acceptable wettable lens surfaces without application of a plasma surface treatment. However, materials such as EVOH materials are expensive, which negatively impacts production costs, and molds made of EVOH typically are harder and more brittle than would be ideal, which negatively impacts lens yields. Also, due to the high level of adhesion typically seen between EVOH molds and silicone hydrogels, it can be difficult if not impossible to dry demold and/or dry delens a silicone hydrogel lens body molded in EVOH, which can further increase manufacturing costs and reduce lens yields.
In view of the above, it can be appreciated that a need exists for contact lens molds comprising new types of materials for cast molding silicone hydrogel ophthalmic lenses using UV light to cure the lenses, new silicone hydrogel ophthalmic lenses cast molded and UV light cured using molds comprising these new types of materials, and associated manufacturing methods that use less expensive, more process-friendly molding materials. For example, these associated manufacturing methods may not require the use of expensive processing steps such as, for example, “wet” demolding steps, both “wet” demolding and “wet” delensing steps, and organic solvent-based washing steps, and which can produce high yields of ophthalmically acceptably wettable silicone hydrogel lens bodies, such as lens bodies which are ophthalmically acceptably wettable without application of a surface plasma treatment, without the presence of an interpenetrating network of a polymeric wetting agent, or both.
All publications, including patents, published patent applications, scientific or trade publications and the like, cited in this specification are hereby incorporated herein in their entirety.